1. Technical Field
The present invention relates to an external-cavity laser light source apparatus with a wavelength converter.
2. Related Art
In recent years, a high-efficiency laser light source apparatus is used in some cases as the illumination light source for projectors, monitoring apparatuses and the like. One example of such a laser light source apparatus has a wavelength converter made of a nonlinear optical crystal or the like, which wavelength-converts infrared light into visible light (green or blue light, for example) as the exit light (see JP-A-2006-100772).
The laser light source apparatus with a wavelength converter described above is configured, for example, in such a way that the light emitted from a laser light source (a semiconductor laser array and a solid state laser apparatus, for example) resonates in a cavity located outside the laser light source and the amplified, more intense laser light is emitted. In such an external-cavity laser light source apparatus, the wavelength converter wavelength-converts part of the light emitted from the laser light source and outputs the converted light to the outside. On the other hand, the light that has not been wavelength-converted in the wavelength converter (non-converted light) is reflected off a mirror that is part of the external cavity, again incident on the lasing medium, and used for amplification. However, when the non-converted light is incident on the wavelength converter in the return path of the external resonance, part of the incident light is wavelength-converted, and the wavelength-converted light incident on the lasing medium is not used for amplification but absorbed therein. It is therefore difficult to efficiently use the wavelength-converted light as an illumination light source.